In a coating area, a top coat is usually applied over an intercoat (or underlying coat) at complete hiding, i.e. to cover up the same. At this time, since the hiding power differs considerably from pigment to pigment, the actual top coat thickness likewise varies in a considerable range from coating to coating. If a low hiding paint composition whose hiding power is in the order of about 50.about.250.mu. as expressed herein in terms of film thickness required for hiding the JIS contrast chart (reflectance of white substrate: Rw=80.+-.1%; reflectance of black substrate: RB.ltoreq.2%) by the visual judgement, is to be applied as a top coat, repeated and somewhat complicated coating operations are always required. This also means the process is very time consuming and hence is not practicable.
Even in the case using a higher hiding paint composition, if the substrate is of a complicated structure and there are hidden portions on the substrate which make it difficult to thoroughly coat the substrate, it is not possible to cover up the whole area equally and there often results a lack of hiding from portion to portion. If one wishes to effect complete hiding, then there results a problem of sagging at the other portions because of excessive coating applied thereupon. Therefore, it is very difficult to hide thoroughly the intercoat with a normal coating application thickness of 30 to 40.mu..
On the other hand, a highly chromatic coating has been welcomed in the market in recent years. Since most of the organic pigments used in such coating have fairly low hiding power, considerable quantities of such pigment must be added to the top coat composition providing resulting in complete hiding on the intercoat with a film thickness of about 30.about.40.mu.. Employment of such a larger quantities of pigment, however, may cause additional problems, under normal conditions, in that the painted film lacks gloss the painting composition becomes highly viscose and the coating exhibits poor weather resistance. Therefore, in such a case we cannot help but use coatings which incompletely hide the substrate to some extent, and for this reason, we are forced to select the same or a somewhat similar colored intercoat for a given colored top coat. However, there is no established selection standard of such intercoat and therefore, at the time when each different kind of pigment is to be used in the intercoat and in the top coat, we cannot but rely on a trial and error system for determining the appropriate color combination. Such procedure is indeed a time-consuming and inefficient one.
Furthermore, since the colored intercoat does include a higher concentration of pigment of the same, or substantially the same hue as with that of the top coat, there is a serious problem of raising up the cost as a matter of course. Therefore, if an appropriate intercoat color, which exhibits a small color difference between a composite coating having a top coat of low hiding power applied at 30.about.40.mu. thickness, i.e. so as to exhibit incomplete hiding characteristics, over the intercoat and a coating having the same top coat applied at complete hiding, can be easily determinable from a wider range of colors. This would be highly advantageous in many ways. Thus, it would be only beneficial in widening the color gamut of the top coat, thereby opening the way for making use of such low hiding pigments previously believed to be unsuitable for use as a top coat because there was no known color which was adequate for intercoat, and also useful in shortening the time duration required for the selection of an appropriate intercoat color for a given top coat, for lowering the cost of inter and top coats due to decreasing the amount of the pigment and shortening the application time or the like.
This invention has been made to overcome the aforementioned disadvantages.